The overall emphasis of this research is to discover patterns of gene expression that affect the health of individuals subjected to chronic chemical exposure. This provides a framework to understand basic biological responses to environmental stress and toxicants and identifies genes that are markers of chemical exposure. The challenges are to identify those genes that respond to toxicant exposure, to discover novel gene interactions and to improve knowledge of complex regulatory networks and cross-communication between different pathways in both health and disease. Concern about the adverse effects of environmental pollutants results from evidence that these chemical pollutants are affecting the health of individuals. However, not all individuals are affected equally: within populations, individuals show variable susceptibility to chemical exposure. Often, the molecular basis for this difference is unknown. This research will use microarray analyses of natural populations to 1) identify genes and patterns of gene expression that are affected by environmental chemicals and 2) examine individual differences in toxic responses. Elucidating the molecular mechanisms underlying biological effects of environmental chemical exposure is important both to understand the responses of animals to chronic chemical exposure and to identify molecular markers of susceptibility associated with increased risk in populations of animals, including humans. Analyzing a variety of different individuals within natural populations is important to identify factors associated with variation in susceptibility. Importantly, non-random patterns of gene expression within and between the polluted populations will be identified. These patterns will provide indices of pollutant exposure in other polluted populations. [unreadable] [unreadable] [unreadable]